DMR-9419257 Marchetti This project addresses several theoretical aspects of nonequilibrium superconductivity and nonlinear collective transport. Vortex arrays pinned by extended defects, such as twin boundaries, are studied. The hydrodynamics of flux- line liquids will be derived and applied. Specific models for flux lattices are studied to understand the general features of collective nonlinear dynamics and transport in driven disordered systems. Also, the dynamics of topological defects produced when a systems is quenched from a disordered to an ordered phase across a symmetry breaking transition is also included as a new direction of research. %%% This project concerns, in part, a theoretical analysis of arrays of linear defects found in high temperature superconductors. This understanding should contribute to the goal of controlling the energy loss present in a variety of applications of these materials. The study of these defects and how they move should also have applications to other classes of materials which are currently of interest in the laboratory. A close collaboration with experimentalists and theorists at Argonne National laboratory is planned as part of this work.